Yes Mitch, you're missing a few things.
(I have an auto.)
A shifter. A different ratio rear axle.
An electronic transmission control module.
Wiring if needed for the above.
Wiring for the shift position/neutral safety
switch.
If stock carb, you need idle-up dashpot,
wiring, solenoid and wiring to the ECU.
Maybe different ECU?
A wider brake pedal/removal of the clutch pedal.
A kick down switch on the accelerator.
The dipstick tube and steel lines to the radiator.
The engine block rear plate may be different.
Hopefully the pilot bearing is not in the
way of the torque converter.
If header, will probably hit the
bell housing.
Make sure your radiator's transmission
cooler is clean and in good shape..
Technically you need the electronic in-tank fuel pump, plus fuel pump control module.
I'm sure I'm forgetting things...
Short answer, you need an auto
transmission truck!